Add UMA for studying download cancellation reasons

chrome/browser/android/download/download_manager_service.cc

Index: chrome/browser/android/download/download_manager_service.cc
diff --git a/chrome/browser/android/download/download_manager_service.cc b/chrome/browser/android/download/download_manager_service.cc
index ab9b1fd7c28f3494ebedce06e5697fdd533d14fe..0036edc7d356a9d6469256d38d9b0d853c98df89 100644
--- a/chrome/browser/android/download/download_manager_service.cc
+++ b/chrome/browser/android/download/download_manager_service.cc
@@ -20,6 +20,7 @@
 using base::android::JavaParamRef;
 using base::android::ConvertJavaStringToUTF8;
 using base::android::ConvertUTF8ToJavaString;
+using content::DownloadControllerAndroid;
 
 // static
 bool DownloadManagerService::RegisterDownloadManagerService(JNIEnv* env) {
@@ -43,7 +44,7 @@ DownloadManagerService::DownloadManagerService(
     jobject obj)
     : java_ref_(env, obj),
       is_history_query_complete_(false) {
-  content::DownloadControllerAndroid::Get()->SetDefaultDownloadFileName(
+  DownloadControllerAndroid::Get()->SetDefaultDownloadFileName(
       l10n_util::GetStringUTF8(IDS_DEFAULT_DOWNLOAD_FILENAME));
 }
 
@@ -75,8 +76,14 @@ void DownloadManagerService::CancelDownload(
     JNIEnv* env,
     jobject obj,
     const JavaParamRef<jstring>& jdownload_guid,
-    bool is_off_the_record) {
+    bool is_off_the_record,
+    bool is_notification_dismissed) {
   std::string download_guid = ConvertJavaStringToUTF8(env, jdownload_guid);
+
+  DownloadControllerAndroid::RecordDownloadCancelReason(
+      is_notification_dismissed ?
+          DownloadControllerAndroid::CANCEL_REASON_NOTIFICATION_DISMISSED :
+          DownloadControllerAndroid::CANCEL_REASON_ACTION_BUTTON);
   // Incognito download can only be cancelled in the same browser session, no
   // need to wait for download history.
   if (is_off_the_record) {
@@ -191,6 +198,8 @@ void DownloadManagerService::OnResumptionFailed(
   base::MessageLoop::current()->PostTask(
       FROM_HERE, base::Bind(&DownloadManagerService::OnResumptionFailedInternal,
                             base::Unretained(this), download_guid));
+  DownloadControllerAndroid::RecordDownloadCancelReason(
+      DownloadControllerAndroid::CANCEL_REASON_NOT_CANCELED);
 }
 
 void DownloadManagerService::OnResumptionFailedInternal(